1. Field of the Invention
The present invention relates generally to a roll-up or curtain type door, and more particularly to an improved roll-up door for use in large doorways, the door of the present invention having an improved support apparatus, an improved spring mounting mechanism, and a unique bearing block which also functions to support the door as it is rolled up.
2. Description of the Related Art
Buildings ranging in size from mini-warehouses or mini-storage facilities to huge warehouses with entrances sufficiently large to admit large trucks require a secure, lockable door which may be easily opened, and which does not require an inordinate amount of space either for the door itself or for the room required to open and close it. Conventional doors for the most part are not useable in such applications since they are either too small or too unwieldy to be acceptable. Roll-up or curtain doors represent a convenient way to provide an easily operable security closure, and they are able to do so in a fairly limited space.
Roll-up doors are typically constructed using one or more sheets of relatively thin metal which are formed by stamping or rolling to provide a plurality of horizontal corrugations extending the entire width of the door. This construction allows the door to be rolled up as it is raised for opening, thereby allowing the door to be stored in a cylindrical configuration at the top of the door opening. Vertical guide tracks, which may be made of extruded aluminum or formed galvanized steel, are typically mounted at opposite sides of the door opening and serve to guide the door as it moves up and down.
The top of the formed metal sheet is fastened to a barrel assembly which is typically constructed with a heavy wall, steel torque tube axle which supports thereon two or more galvanized steel drums or wheels. The barrel assembly is rotatably mounted between two brackets located slightly above the upper corners of the door opening. The barrel assembly is biased by one or two tempered steel torsion springs to balance the weight of the roll-up door, thereby allowing the door to be easily raised or lowered in a simple one-hand operation. Adhesively affixed tapes typically extend along the inner face of the door where contact is made with the galvanized steel drums or wheels to protect the door against wear by the galvanized steel drums or wheels, and to avoid rubbing of the successive layers of the roll-up door against each other.
Such doors also typically have a locking mechanism mounted thereon, which may be a simple sliding bolt type lock. With this mechanism, when the door is closed the bolt slides into a locking engagement with the guide track or with other metal means which prevents the door from being opened unless the bolt is opened. A simple padlock may then be used to lock the bolt assembly.
This type of roll-up door is easy to operate, and will provide years of dependable service with virtually no maintenance. Such doors are relatively inexpensive and relatively easy to manufacture, although the business of constructing such doors is a highly competitive one. Accordingly it is desirable to provide a high degree of quality and reliability while minimizing the cost of manufacturing the doors. Minimizing the quantity of hardware components is always desirable, both from a cost standpoint and from a desire to minimize the number of parts and by so doing the amount of assembly required.
While such roll-up doors are relatively easy to construct for smaller door openings, there are several particular problems which are encountered when designing such a door for a large door opening such as a warehouse door through which large trucks and trailers will pass. Such warehouses commonly have doorways which are twenty feet tall, and correspondingly wide. It will at once be appreciated by those skilled in the art that there are two problems directly attributable to the size of the door.
First, the weight of the formed metal curtain door is supported by the barrel assembly at the two ends thereof, creating a flexural stress in the torque tube of the barrel assembly. Particularly when the formed metal curtain door is rolled up and the load is the heaviest, the torque tube will flex, causing a bowing of the door which requires the metal of the formed metal curtain door to flex as well. This is undesirable, as is the possibility of a fracture of the torque tube supporting the door. In the event of such a fracture, the heavy door and barrel assembly would come down with likely serious consequences.
In addition, with tall doors another problem is inherent in the design. The diameter of the barrel assembly will vary considerably between a minimum when the door is fully down, and a maximum when the door is up and the long formed metal curtain door is wound around the barrel assembly. This creates considerable problems in the mounting of the barrel assembly, since it must be mounted sufficiently far from the interior wall to allow the formed metal curtain door to roll up on the barrel assembly. When the formed metal curtain door is fully down, considerable space will exist between the barrel assembly and the guide tracks, an undesirable situation due to the gap which must be left between the door header and the door.
Another fundamental problem inherent in the design of large roll-up doors is the high risk of spring failure. In such doors, one or more springs are each mounted to an axle extending through the torque tube at one end, and to the torque tube or drums of the barrel assembly at the other end. Thus, both ends of the springs are fixedly mounted, leaving no room for longitudinal shrinkage or expansion. This greatly increases the likelihood of spring breakage, particularly at the ends thereof where the springs are retained. When spring breakage does occur, typically the entire barrel assembly must be shipped to the factory for spring replacement since the springs are located inside the torque tube.
An additional problem with large roll-up doors is the fact that the adhesively affixed tapes extending along the inner face of the door where contact is made with the galvanized steel drums or wheels are simply not sufficient in view of the weight of the formed metal curtain door when it is rolled up. The corrugations of the formed metal curtain door thus tend to nest and/or crush each other as the door is rolled up or down. In order to achieve the objectives of durability and long life, it is apparent that another arrangement is necessary.
Such large doors also exhibit poorer sealing than smaller doors, allowing air to flow more or less freely around the edges of the door. As such, the sealing characteristics of such large roll-up doors have been rather poor, an undesirable weak point not acceptable to most warehouses.
It is accordingly a first primary objective of the present invention that it provide a substantially stronger barrel assembly design. The improved design must be substantially less susceptible to flexural stress than are presently known doors. In addition, the improved barrel assembly design should be designed in a manner which increases the strength thereof without greatly increasing the weight of the barrel assembly, since the barrel assembly must be supported at the top of the door assembly.
It is a second primary objective of the present invention that it mount the barrel assembly in a manner whereby the variation in diameter of the barrel assembly does not affect the performance of the door. In achieving this objective, it is desirable to mount the barrel assembly no further from the interior surface of the wall than is absolutely necessary.
It is a third primary objective of the present invention to mount the springs used in the barrel assembly in a manner allowing for longitudinal expansion and shrinkage. By so doing, the likelihood of catastrophic breakage of the springs is greatly reduced. It is a correlated objective to make the barrel assembly serviceable by the user in the event of spring breakage, thus obviating the need to send the barrel assembly to the factory for repair.
It is a fourth primary objective of the present invention to provide a mechanism for supporting the formed metal curtain door as it is rolled onto the barrel assembly. This mechanism must protect the formed metal curtain door against damage caused by nesting of the corrugations and the weight of the formed metal curtain door.
In accordance with an additional objective, it is desirable to provide a sealing mechanism to prevent air from flowing around the edges of the door when it is in its lowered position. In a further additional objective, the clips which support the guide tracks should be reversible. It is also an objective to make the resulting roll-up door as durable and long-lasting as is possible, while simultaneously making it economic of construction to afford it the greatest possible economic advantage over competing doors. Finally, it is also an objective that all of the aforesaid advantages and objectives be achieved without incurring any substantial relative disadvantage.